Urgent: cannot edit article anymore

Dear Unsal, Today I tried to create a new a new article on two of my FirmaSIte Base related sites (portal.spd-fn.de and christineheimpel-fn.de)

On both sides the editor doesn’t work anymore. I can open the article, sometimes I’m able to put content into the ‘normal’ content part, but even then: switching between text and visual mode does not work. I can add a textblock or any other block – but it doesn’t let me edit or add anything in this block. Neither header nor text.

I tried to switch from childtheme to basetheme – no effect. I’m running the actual wp-Version.

Addition: Even if I switched off all plugins the behaviour is the same. Really strange: Sometimes I can edit or add a new block and edit it, than suddenly: not. This behaviour is shown on several different hosts, even on my local MAMP Installation. It occurs on Safari and in Firefox

For those who have similar problems: To delete the firmasite plugin I first had to switch to a non firmasite theme, then the plugin reacted to ‘deactivate’ and ‘delete’, then to switch back to firmasite theme.